Line type inkjet printing apparatuses include a general line type inkjet printing apparatus using one line head for one color ink, and a line type inkjet printing apparatus using plural line heads for one color ink, and forming an image by dividing image data into pieces corresponding to the plural line heads. In the latter line type inkjet printing apparatus, the plural line heads share the work of forming an image. This apparatus can therefore achieve a speedup in printing since it enables printing operation beyond the maximum driving frequency of one line head, that is, the printing at a speed proportional to the number of line heads.
In a line type inkjet printing apparatus, one line head may have a poorly ejecting nozzle (hereinafter also referred to as a “faulty nozzle”) incapable of ejecting ink normally for some reason or other. Under this condition, in a case of the general line type inkjet printing apparatus, one of the following two approaches can be taken: one of the approaches is to continue to print, without ensuring printing quality; and the other is to suspend printing to replace the line head having the faulty nozzles with a new one. In contrast, in a case of the line type inkjet printing apparatus using the plural line heads for one color ink, another approach can be taken in addition to the above approaches, and this approach is to continue to print by using only normal line heads having no faulty nozzles. Moreover, there is also a technique allowing plural line heads for one color ink to perform complementary operations when a faulty nozzle is detected, that is, allowing each of the plural line heads to eject ink complementarily by using only normal nozzles (see Patent Document 1).
The line type inkjet printing apparatus using the plural line heads for one color ink, however, is originally configured to meet a demand for high-speed printing. The approach of using the normal line heads alone to continue to print, however, cannot satisfy the demand for the high-speed printing because a printing speed is inevitably decreased up to the speed proportional to the number of normal line heads. Here, consider a case where the technique disclosed in Patent Document 1 is applied when a faulty nozzle is detected in a printing apparatus. In this case, in order for normal line heads to complementarily eject ink, the printing apparatus has to re-arrange print data and generate mask data, and further requires means for storing the generated mask data. The above technique therefore has the problem of enlarging the scale of circuitry of the printing apparatus because of rendering the mode of control and the configuration of a control system complicated.
[Patent Document 1] Japanese Patent Laid-Open No. 10-6488 (1998))